Field of the Invention
The present invention concerns a method to operate a magnetic resonance imaging apparatus in order to acquire multiple images in a session, wherein a reference scan is acquired that is used by the technician implementing the imaging session to ensure that all of the images in the session are acquired so as to be consistent with prescribed imaging conditions. The invention also concerns a magnetic resonance imaging apparatus to implement such a method.
Description of the Prior Art
Before acquiring a magnetic resonance (MR) diagnostic image (i.e., an MR image having an image content and quality of a sufficiently high level to permit a reliable medical diagnosis to be made therefrom), it is common to first acquire a localizer or scout (reference) scan of the examination subject. The technician operating the MR apparatus uses such a reference scan to manually set or adjust one or more imaging parameters, including positioning of the examination subject, based on the content of the reference image. The reference image need not be of the same image quality as the diagnostic image that is subsequently generated, and thus may be acquired, for example, with lower resolution and thus with a shorter acquisition duration than is the case for the diagnostic image.
In a scan session wherein multiple MR images are acquired, it is conventional to acquire one reference image and to use the same reference image to review the imaging conditions for all of the scans throughout the session. Such a session may last up to an hour or more, and therefore it is very likely, unless patient movement is restricted in some manner, that the patient will move during the scan session. This causes the reference image, which was obtained at the beginning of the scan session, to no longer be consistent with the actual patient position that exists at a later time in the session, and therefore images obtained later in the session, wherein imaging parameters and/or the patient position have been set using this no longer accurate reference scan, may also be inaccurate.
Such a reference scan is often used in particular to set the spatial position or extent of a slice of the examination subject, from which image data are to be obtained.
Automated slice positioning techniques are known, but the same problem described above persists therein, because the reference data for the automated slice positioning technique is acquired at the beginning of the scan session, and is not repeated or adjusted during the scan session.
Motion-corrected scans are also known, wherein a real time motion correction is implemented, such as EPI and 3D PACE. In such motion-corrected scans, the reference for motion correction is typically acquired at the beginning of each motion-corrected scan. In a multi-series scan session, this means that such a motion reference is acquired a number of times that is equal to the number of scans in the scan session, which can extend the time duration of the overall session.